From the author's README on Thunderstore

Black Knight Shield - Back Bling

A fan-made back bling that brings the Black Knight's dragon shield from Fortnite to skate. through ReSkate. It sits on your upper back with the dragon facing out.

Install

Install with the Thunderstore Mod Manager (ReSkate community), then pick it in the character customizer (Outfits).

Notes

Built with ReSkate Studio on a onesie outfit slot; the onesie itself is removed, only the shield is left.
The shield is rigid and follows your upper back, sitting close without clipping when you crouch, twist or raise your arms.
Original shield texture, matte finish (no shine), no outfit pattern tint.
Wear it with any top; it sits just behind the shirt.
Targets the skate. build recorded in .reskate-studio-patch. If the game updates, the mod may need a rebuild.

Credits

Port to skate. / ReSkate: devinzzc
Original design: Black Shield back bling, Fortnite © Epic Games.

This is an unofficial fan tribute. It is not affiliated with or endorsed by Epic Games, Electronic Arts or Full Circle. If you are a rights holder and want it removed, contact the uploader.

Install Black Knight Shield

You need ReSkate and your own copy of skate. on Steam.

Open ReSkateLauncher.exe and go to MODS.
Search for Black Knight Shield and click install. The launcher also installs anything it depends on.
Press PLAY. In game, the MODS tab of the ReSkate menu (Insert) turns it on and off.

Or install it by hand: download the .zip and drop it on the launcher window, or unzip it into its own folder in Mods\ beside Skate.exe.

Maps show up in the ReSkate menu's level list. To join a server running a custom map, you need the same map installed. If the game won't load after installing, see known issues.

skatemods doesn't host or review this mod. The download comes straight from Thunderstore. Only install mods you trust, because scripts can run code.